The invention relates to improvements in apparatus for transferring sheets, panels, plates and like flat or substantially flat commodities, and more particularly to improvements in apparatus for transferring sheets and/or like commodities which are supplied to a transfer station in the form of stacks of overlapping commodities.
It is often necessary to transfer individual sheets, panels, plates or analogous commodities from a magazine to one or more spaced-apart locations. For example, it is customary to draw individual sheet-like commodities from a stack in a magazine for delivery to one or more conveyors which, in turn, advance successively withdrawn individual commodities to a station where the commodities are merged into, added to and/or otherwise associated with layers, piles or other accumulations of identical and/or different commodities. The transferred commodities can constitute front or back covers for books, pamphlets, brochures, pads or other stationery products, but such commodities can also constitute dividers for use in various types of loose leaf books, pads, catalogues or the like. Still further, the commodities can constitute pockets, advertising literature, separators, top or bottom sheets of reams of typewriter paper sheets, copy paper sheets and/or others.
The commodities can be made of paper, cardboard, plastic sheeting or paneling or combinations of two or more layers such as laminates containing two or more plies of paper, plastic, cardboard and/or metal.
The transfer of commodities in the form of sheets or the like from a stack in a magazine to a processing location does not present many problems if the thickness of each commodity is constant and if the commodites have identical sizes and shapes. However, it is much more difficult to properly transfer, at a high or very high frequency, individual commodities (e.g., in the form of pockets) having plural layers of different sizes, thicknesses and/or shapes. Thus, if the mechanism for transferring discrete commodities is designed to remove successive commodities from a stack, the dimensions of the stack are limited (i.e., the stack cannot contain a relatively large number of overlapping commodities) because the stability of a stack of commodities each of which includes (or at least some of which include) at least one relatively thick portion and a relatively thin portion is nil or close to nil as soon as the height of the stack reaches a relatively low value. Therefore, and if the commodities are to be drawn from a magazine which contains a stack of overlapping commodities, the magazine must be refilled at frequent intervals in order to avoid collapsing of stacks (consisting of commodities having portions of greater thickness and portions of lesser thickness) in the magazine proper, during introduction of stacks into the magazine or at the location of assembly of such commodities into stacks. Moreover, the operation of such apparatus must be continuously monitored by one or more persons in order to avoid unsatisfactory transfer of commodities from the magazine, unsatisfactory introduction of stacked commodities into the magazine, unsatisfactory gathering of commodities into stacks during introduction into the magazine or unsatisfactory formation of stacks outside of the magazine.
U.S. Pat. No. 3,073,460 granted Jan. 15, 1963 to Richert et al. for "Equipment for continuously charging an edgewise conveying system" discloses an apparatus wherein compression fingers affixed to two endless chains define a series of spaces for sheets which are to be advanced into the range of a suction-operated separating device. A drawback of the patented apparatus is that the compression fingers cannot adequately control the movements of sheets during advancement of sheets all the way to the separating device. Reasonably reliable guidance of the sheets is ensured only after the sheets leave the path of the compression fingers and advance along a stationary platform into the range of the separating device.
Swiss Pat. No. 473 724 granted Jun. 15, 1969 to Stobb discloses an apparatus for lifting a succession of stacks of paper sheets toward a withdrawing device which removes sheets from the top of the stack below it. Such stack is lifted by a plate which provides room for introduction of a fresh stack below it as soon as the bottom part of the expiring stack has risen to a preselected level. This apparatus cannot manipulate tall stacks of sheet-like commodities having portions of different thicknesses.
German patent application Serial No. 27 32 837 of Himmelsbach (published Feb. 8, 1979) discloses an apparatus for accumulating stacks of overlapping sheets on a platform between successive pairs of separators which advance past a rotary sheet-supplying conveyor. The inventor named in the German patent application wishes to gather coffee bags and like commodities into relatively small stacks each of which is to contain a given number of commodities.